Operation of an engine may be improved by providing detection and error-mitigation systems. Various systems have been developed to attempt to detect negative engine conditions. Some of these systems are completed only through service diagnostic testing. Further some systems only detect the engine degradation condition after the engine degradation event has occurred. Moreover, many of these systems do not provide a mitigation strategy to fully address and compensate for the detected engine condition.
As an example, preignition is an engine degradation event which may have substantial negative effects on engines. Preignition generally is in-cylinder combustion initiated prior to activating the spark plug and may result in extremely high cylinder pressures and temperatures. The high pressures and temperatures may result in damage to the engine. For example, in-use engine degradation may be attributed to preignition. Moreover, preignition may affect engine durability. To avoid or reduce the dangers of preignition, engines may be designed to accommodate potential engine damage due to preignition. Such designs may prevent the engine from being designed to optimize engine performance, e.g., by increasing engine size, weight, material costs, etc.
The inventors herein have recognized that without the ability to detect and mitigate preignition, the fuel economy and performance of the engine may be compromised to insure some margin of safety from preignition. Adopting preignition detection and providing effective mitigation of such preignition may reduce in-use engine degradation. Further, preignition detection and mitigation may facilitate design and calibration of engines closer to optimum performance.
Therefore, in one approach, a system and method may be provided which mitigates the effects of preignition by using spark plug ionization detection to detect preignition on a cycle-by-cycle basis for each cylinder. Once pre-ignition has been detected, the engine control system can be programmed to avoid or reduce engine damage by: 1) deactivating the fuel injector on the cylinder in which preignition was detected (while continuing operation of remaining fuel injectors); 2) retarding spark (and/or adding additional fuel enrichment) for the remaining firing cylinders preventing additional cylinders from entering preignition; 3) activating a user indicator system; and 4) after a period, reactivating the injector for the cylinder in which the preignition was detected.